1904.] The Chemical Dynamics of Photographic Development. 459 

 Another batch of the same emulsion gave 



Series I K = 0-0191, 



II K = 0-0201, 



Series III 0-0217, 



IV.. 0-0204. 





Total mean 0*0204, 



Total mean of four series... K = 0'0203. 



The following table and curve show that the expression is satis- 

 factory ovefr a wide range of development, considering the experimental 

 difficulties. All the series, DI, D 2 , and D 3 , were reduced by common 

 proportion to the same value : 



Table V. Curve for N/500 Br and N/25 Ferrous Oxalate. 



1-5 



i-o 



Race of development/ 



o 20 



Time in mins. 



40 60 



Curve calc. 



80 



120 



140 



It appears that generally the value of K is constant for a standard 

 emulsion freshly coated. Variations, however, may be caused by 

 different emulsification, and the value varies with different plates. 



